The present invention relates generally to the art of surfactants, and more particularly to the art of surfactants in polyurethane foams.
U.S. Pat. No. 5,308,881 to Londrigan et al. discloses a closed cell, rigid polyisocyanurate foam which comprises the reaction product of a polyisocyanate and a polyol in the presence of a hydrogen-containing blowing agent, and a siloxane oxyalkylene copolymer having a molecular weight below 7500 and an oxyalkylene portion containing greater than 60 weight percent of oxyethylene units. The siloxane oxyalkylene copolymer is prepared by the reaction of an organohydrogen siloxane with a polyoxyalkylene in an essentially solventless system or in the presence of a high boiling point polar polyol.
Insulating foams such as polyurethanes and polyisocyanurates have historically used chlorofluorocarbons (CFCs) as blowing agents, i.e. gases generating bubbles to create cell structures in the polymer network to form a foam. With increasing concerns about the environmental effects of CFC use, which have been linked to ozone depletion and global warming, and impending bans on many uses, foam producers must find alternate blowing agents. Unfortunately, the current non-CFC candidates, hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs), have higher thermal conductivities and so are less effective than CFCs, resulting in less insulating capacity for foams produced using them as blowing agents. Thus as CFC use in foams is phased out in accordance with Environmental Protection Agency (EPA) regulations, foam producers must find ways to improve the insulating values of foams produced with less thermally effective alternate blowing agents because demand for energy efficiency is concurrently increasing, whether it relates to energy consumption of refrigerators or home heating and cooling.
The thermal conductivity (K-factor) of a porous material, such as polyurethane foam, is the sum of the conductivity through the solid phase, the conductivity through the gas phase, conductivity attributed to radiational transfer, and conductivity attributed to convection, which is generally less significant. For polyurethane foams, K.sub.f =K.sub.s +K.sub.g +K.sub.r, i.e. the thermal conductivity of the foam (K.sub.f) is equal to the thermal conductivity through the solid polymer phase (K.sub.s), plus the thermal conductivity through the gas in the foam cells (K.sub.g) and the thermal conductivity through radiative heat transfer (K.sub.r), which may be as high as 30 percent of total thermal conductivity.